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T1-F Interface 143
T1-F Interface T1-F interface is fractional T1 interface, and it is respectively simplified CT1/PRI
interface. If there is no need to use multiple channel sets or if ISDN PRI is not
necessary in an T1 application, it is too much to use CT1/PRI interface. At this time,
T1-F interface is more than enough for meeting the simple T1 access
requirements. Compared with CT1/PRI interface, T1-F interfaces is a nice low-cost
choice for T1 access.
Compared with CT1/PRI interface, T1-F interface has the following features:
■ When working in framed mode, T1-F interface can only bind time slots into
one channel set, but CT1/PRI interface can group timeslots randomly and bind
them into multiple channel sets.
■ T1-F interface does not support PRI operating mode.
T1 line comprises 24 multiplexed channels. That is, a T1 primary group frame DS1
(Digital Signal Level-1) comprises 24 DS0 (64kbps) time slots, each has 8 bits and 1
framing bit for synchronization, and thus each primary group frame has 193 bits
(24 X 8+1). As DS1 can transmit 8000 frames per second, its transmission speed is
193 X 8k = 1544kbps.
T1-F interface can only work in framed mode, and it can randomly bind all time
slots (time slots 1 through 24) into one channel set. T1-F interface has the rate of
nx64kbps or nx56kbps, owns logical features of synchronous serial interface, and
supports the data link layer protocols PPP, HDLC, Frame Relay, LAPB and X.25 as
well as the network protocols IP and IPX.
Configure T1-F Interface T1-F interface configuration includes:
■ Enter the view of a specified interface
■ Set interface rate after binding operation
■ Set length/attenuation of transmission line
■ Set line code format
■ Set line clock
■ Set interface frame format
■ Enable or disable local/remote loopback
1 Enter the view of a Specified Interface
Unlike CT1/PRI interface, T1-F interface has no Controller view. The system identify
a T1-F interface as a synchronous serial interface, so entering the view of T1-F
interface is equivalent to entering the view of the corresponding serial interface.
Perform the following configuration in all views.
Table 156 Enter the view of an T1-F interface
T1-F interface is sequenced based on the same numbering and are numbered
together with the synchronous serial interfaces. For example, insert one 1E1-F
module in slot 0 on a 3Com Router, one 4SA module in slot 1, and two 1T1-F
Operation Command
Enter the view of a T1-F interface interface serial
serial-number